question about domain

Hi,
So here are my class :

class task(osv.osv):
    _name = "project.task"
    _inherit = "project.task"
    _description = "Tasks"
    _date_name = "date_start"
    _columns = {
        'recurring':fields.boolean('Recurring'),
        }
    _defaults = {
        'recurring': lambda *a:'False',
        }
    _order = "sequence, priority, date_deadline, id"
task()

class test_contracts(osv.osv):
 _name = 'test.contracts'
 _columns = {
  'title': fields.char('Title', size=40, required=True),
  'date_contracts': fields.date('Date', required=True),
  'task_id': fields.one2many('project.task','parent_id','task'),
 }
test_contracts()

And my view :

 <record model="ir.ui.view" id="view_test_contracts_form">
   <field name="name">Contracts</field>
   <field name="model">test.contracts</field>
   <field name="type">form</field>
   <field name="arch" type="xml">
  <form string="Contracts">
   <notebook position="inside">
   <page string="General">
    <field name="title" select="1" />
    <field name="date_contracts"/>
   </page>
   <page string="Task">
    <field name="task_id" nolabel="1" mode="tree,form" colspan="4" position="replace" select="1" domain="[('recurring','=',True)]">
      <tree string="Tasks">
        <field name="name"/>
        <field name="recurring" select="1" domain="[('recurring','=',True)]"/>
      </tree>
      <form string="Task edition">
        <group colspan="6" col="6">
          <field name="name" select="1" attrs="{'readonly':[('state','=','done')]}" />
          <field name="recurring" select="1" />
        </group>
      </form>
    </field>
   </page>
   </notebook>
  </form>
   </field>
 </record>

Everything is working exept the domain, and I'm trying to find why since 3 days... Does anybody have an idea to help me please ?
Thanks =)